Field of the Invention
The present invention relates to a diffusion light distribution optical system and a vehicle lighting apparatus. Specifically, the present invention relates to a diffusion light distribution optical system used in combination with a light source and a vehicle lighting apparatus including the diffusion light distribution optical system.
Background
In the related art, vehicle lighting apparatuses including a light source in combination with a lens body have been proposed (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2004-241349 and Japanese Patent No. 4068387). In the vehicle lighting apparatus, light from a light source is incident on an incidence surface of the lens body to enter the inside of the lens body, and part of the light is reflected by a reflection surface of the lens body. Then, the light is emitted to the outside of the lens body from an emission surface of the lens body. Thereby, the light emitted frontward of the lens body forms a low beam light distribution pattern which is a reverse projection of a light source image formed in the vicinity of a focal point of the emission surface of the lens body and which has an upper end edge including a cutoff line defined by a front end part of the reflection surface.